Device and method for clamping and wire-bonding the leads of a lead frame one set at a time

ABSTRACT

A wire-bonding machine includes a heat block for supporting a lead frame during wire-bonding. A clamp mechanism in the machine clamps leads of the lead frame during wire-bonding by fixedly holding sets of the leads against the heat block one set at a time. A wire-bonding tool wire-bonds leads clamped by the clamp mechanism to bond pads on an integrated circuit die. By clamping leads of the lead frame in separate sets, the machine provides improved clamping for lead frames with leads requiring clamping in different planes.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 08/763,366,filed Dec. 13, 1996, now U.S. Pat. No. 6,068,174, issued May 30, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to devices and methods for clamping theleads of a lead frame while the leads are being wire-bonded to bond padson an integrated circuit die.

2. State of the Art

Integrated circuit (IC) dice or “chips” are small, generally rectangularIC devices cut from a semiconductor wafer, such as a silicon wafer, onwhich multiple ICs have been fabricated. IC dice are typically packagedto protect them from corrosion by attaching them to lead frames using asolder or epoxy, electrically connecting them to leads in the leadframes, and then encapsulating the resulting die and lead frameassemblies in plastic die packages. The leads in the encapsulated leadframes protrude from the die packages and terminate in pins so the diceelectrically connected to the leads can communicate with circuitryexternal to the die packages through the pins.

IC dice are typically electrically connected to the leads in theirassociated lead frames in a process known as “wire-bonding.” Duringwire-bonding of an IC die to a lead frame, a wire-bonding tool, such asan ultrasonic, thermosonic, or thermo-compression tool, bonds lengths offine wire to bond pads on the die and to bonding sites on the leads inthe lead frame in order to connect the bond pads and the leads. Thisprocess is well-known, and is described in detail in U.S. Pat. Nos.4,030,657, 4,361,261, 4,527,730, 4,600,138, 4,603,803, 4,765,531,4,778,097, 5,148,959, 5,217,154, 5,251,805, 5,307,978, 5,421,503,5,425,491, 5,445,306, 5,465,899, 5,486,733, 5,513,792, and 5,516,023.

In order to ensure proper wire-bonding, lead frame leads are typicallyclamped during wire-bonding to stabilize them so a solid bond can beformed between the leads and the fine wire used to wire-bond them to anIC die. Without clamping, the leads can move during wire-bonding andcause unreliable bonds to be formed between the leads and the fine wire.

Conventionally, all the leads in a lead frame are clamped at once in asingle plane during wire-bonding, as shown in U.S. Pat. Nos. 3,685,137,5,035,034, and 5,193,733. By clamping all the leads of a lead frame atonce, the conventional clamping method holds to a relative minimum thetime it takes to wire bond an IC die to the lead frame.

While holding wire-bonding time to a minimum is advantageous, theconventional clamping method can also be problematic with certain leadframes. For example, some lead frames, such as the Leads-Over-Chip leadframe shown in U.S. Pat. No. 4,862,245, have leads which extend closerto the bond pads of IC dice attached to the lead frames than other leadssuch that fine wires bonded between the IC dice and these other leadsmust arch over the leads which are closer to the bond pads on the dice.Since fine wires must arch over the leads closer to the bond pads, thecloser leads cannot be clamped at the same time all the other leads areclamped. Instead, the closer leads conventionally remain unclamped, oronly partially clamped, during wire-bonding, resulting in potentiallyunreliable bonds to those leads.

Also, because the conventional clamping method clamps all the leads of alead frame at once in a single plane, it cannot adequately clamp leadsof a lead frame which must be clamped in different planes. For example,as shown in U.S. Pat. No. 4,943,843, some Tape-Under-Frame lead frameshave leads which extend underneath an IC die and then project beyond thefootprint of the die so they may be wire-bonded to bond pads on the die.These leads are typically left unclamped during wire-bonding, becausethey are not clampable in accordance with the conventional clampingmethod in the same plane as the remainder of the leads. As a result,these leads have potentially unreliable wire bonds. In a similarfashion, the conventional clamping method cannot adequately clampmulti-layer lead frames, such as that shown in U.S. Pat. No. 5,291,061.

Wire-bonding clamps, such as that shown in U.S. Pat. No. 4,821,945, havebeen developed to alleviate some of the problems of the conventionalclamping method by clamping leads individually. However, these clampscan dramatically increase the time it takes to wire-bond an IC die,because the clamp must be sequentially indexed to each individual lead.

Therefore, there is a need in the art for a device and method forclamping lead frame leads during wire-bonding that can clamp leads indifferent planes without significantly increasing the time it takes towire-bond an IC die.

SUMMARY OF THE INVENTION

An inventive wire-bonding apparatus includes a base for supporting alead frame during wire-bonding. A clamp mechanism in the apparatusfixedly holds sets of leads of the lead frame against the base one setat a time, with each set including fewer than all the leads and at leastone set including more than one of the leads. Also, a wire-bonding toolwire-bonds leads fixedly held against the base by the clamp mechanism tobond pads on an integrated circuit (IC) die. As a result, leads indifferent planes can be effectively clamped and wire-bonded in separatesets, yet the leads within each set are all clamped at the same time, sothe wire-bonding time for an IC die is kept to a minimum.

Further embodiments include a clamping apparatus which includes the baseand clamp mechanism described above and the clamp mechanism describedabove by itself.

In an additional embodiment, a bonding machine for wire bonding leads oflead frames in a lead frame strip to bond pads on IC dice attached tothe lead frames includes a heat block with a contact area for heatingthe dice and the lead frames. An indexing mechanism indexes the leadframe strip through the bonding machine so each lead frame in the stripis sequentially indexed to the heat block's contact area. A clampmechanism fixedly holds sets of the leads of each lead frame indexed tothe heat block's contact area against the heat block one set at a time,and a wire-bonding tool wire-bonds the leads in each set held againstthe heat block to bond pads on the IC die attached to the lead frame ofthe held leads.

In another embodiment, a bonding machine similar to that described abovesimultaneously clamps and wire-bonds sequential lead frames in a leadframe strip at multiple contact areas on a heat block.

In a still further embodiment, a bonding machine for wire bonding leadsof a Tape-Under-Frame (TUF) lead frame to bond pads on a front-sidesurface of an IC die attached to the TUF lead frame includes a heatblock for supporting and heating the die and the TUF lead frame. A clampmechanism fixedly holds a first set of leads of the TUF lead frame,which extends in a plane of a backside surface of the IC die to supportthe die, and a second set of leads of the TUF lead frame, which extendsin the plane of the frontside surface of the IC die, against the heatblock one set at a time. Also, a wire-bonding tool wire bonds the leadsin each set of leads fixedly held against the heat block to bond pads onthe IC die.

In still another embodiment, a bonding machine for wire bonding leads ofa partial Leads-Over-Chip (LOC) lead frame to bond pads on an IC dieincludes a heat block for supporting and heating the die and the partialLOC lead frame. A clamp mechanism fixedly holds LOC leads of the partialLOC lead frame against the die, and other leads which terminateproximate the perimeter of the IC die against the heat block, atdifferent times. Also, a wire bonding tool wire bonds the fixedly-heldleads to bond pads on the IC die.

In yet another embodiment, a bonding machine for wire bonding bus barand nonbus bar LOC leads of a LOC lead frame to bond pads on an IC dieattached to and supported by the LOC leads includes a heat block forsupporting and heating the die and the LOC lead frame. A clamp mechanismfixedly holds the bus bar and non-bus bar LOC leads against the die atdifferent times, and a wire-bonding tool wire bonds the fixedly-held LOCleads to bond pads on the IC die.

In another additional embodiment, a bonding machine for wire bondingleads of a lead frame to bond pads on an IC die attached to the leadframe includes a heat block for supporting and heating the die and thelead frame. A clamp mechanism fixedly holds a first set of the leads ofthe lead frame, which extend toward the die and terminate proximate thedie's perimeter in a first plane, and a second set of the leads of thelead frame, which extend toward the die and terminate proximate thedie's perimeter in a second plane different than the first, against theheat block at different times. Also, a wire-bonding tool wire bonds thefixedly-held leads to bond pads on the IC die.

In a further embodiment, a method for clamping leads of a lead frameincludes clamping a set of the leads at a time with each set includingfewer than all the leads and at least one set including more than one ofthe leads.

In a still further embodiment, a method for wire bonding leads of leadframes in a lead frame strip to bond pads on IC dice attached to thelead frames includes: sequentially indexing each lead frame in the stripto a clamping position; clamping the leads of each lead frame indexed tothe clamping position one set at a time with each set including fewerthan all the leads of the lead frame and at least one set including morethan one of the leads; and wire bonding each set of clamped leads tobond pads on the IC die attached to the lead frame of the clamped leads.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A and 1B are isometric views of a lead frame clamped andwire-bonded to an integrated circuit (IC) die in accordance with oneembodiment of the present invention;

FIGS. 2A and 2B are isometric views of a Leads-Over-Chip (LOC) leadframe clamped and wire-bonded to an IC die in accordance with anotherembodiment of the present invention;

FIGS. 3A and 3B are isometric views of a partial LOC lead frame clampedand wire-bonded to an IC die in accordance with a further embodiment ofthe present invention;

FIGS. 4A and 4B are isometric views of a Tape-Under-Frame (TUF) leadframe clamped and wire-bonded to an IC die in accordance with anadditional embodiment of the present invention;

FIGS. 5A and 5B are isometric views of a single-piece, multi-level leadframe clamped and wire-bonded to an IC die in accordance with yetanother embodiment of the present invention;

FIGS. 6A and 6B are isometric views of a two-piece, multi-level leadframe clamped and wire-bonded to an IC die in accordance with a stillfurther embodiment of the present invention; and

FIGS. 7A and 7B are isometric views of wire-bonding machines whichincorporate the respective clamping embodiments of FIGS. 2A,2B and5A,5B.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1A, a portion 10 of a clamp mechanism in accordancewith the present invention includes a plurality of clamp members 12moving together as directed by an actuating mechanism (not shown) in awire-bonding machine (not shown) to fixedly hold a first set of leads 14of a lead frame 16 against a heat block or other base (not shown)beneath the lead frame 16. Once the leads 14 are fixedly held (i.e.,clamped) by the clamp members 12, they may be wire-bonded using a wirebond tool (not shown) to selected bond pads on a front-side surface ofan integrated circuit (IC) die 20 attached to the lead frame 16.

As shown in FIG. 1B, the leads 14 of the lead frame 16 have beenwire-bonded to bond pads on the IC die 20 while being clamped asdescribed above and the lead frame 16 has been indexed to a new clampinglocation with respect to the clamp mechanism of FIG. 1A. Another portion22 of the clamp mechanism includes a clamp block 24 moving as directedby the actuating mechanism (not shown) of FIG. 1A to fixedly hold asecond set of leads 26 of the lead frame 16 against the heat block orother base (not shown) beneath the lead frame 16. Once the leads 26 arefixedly held by the clamp block 24, they may be wire-bonded through abonding aperture 28 in the clamp block 24 to bond pads on the front-sidesurface of the IC die 20 using a wire bond tool (not shown).

By clamping the leads 14 and 26 of the lead frame 16 in separate sets inaccordance with the present invention, the leads 14 interposed betweenthe IC die 20 and the leads 26 can be clamped while they arewire-bonded. This is in contrast to the conventional clamping methoddescribed above which would only clamp the leads of the lead frame 16once, and thus would not clamp the leads 14, since to do so while alsoclamping the leads 26 would interfere with the wire-bonding of the leads26.

It will be understood by those having skill in the field of thisinvention that the clamp mechanism of FIGS. 1A and 1B may take a varietyof forms, and that the present invention includes within its scope allclamp mechanisms capable of clamping the leads of a lead frame in sets,one set at a time. It will also be understood that the clamp mechanismmay comprise a variety of clamp members, including, for example, one ormore clamp blocks, as shown in FIG. 1B, or one or more clamp fingers, asdescribed below with respect to FIG. 3B.

It will further be understood that the clamp mechanism may include oneor more clamp members for clamping each set of leads in a lead frame,and that each of the plurality of clamp members may individually clampone or several leads in the set. In addition, it will be understoodthat, although the present invention will be described with respect to aclamp mechanism clamping the leads of a lead frame in two sets in aparticular order, the present invention includes within its scope clampmechanisms which clamp the leads of a lead frame in more than two setsin any order. Further, it will be understood that the present inventionincludes within its scope: clamp mechanisms that clamp all the sets ofleads of a lead frame at different times but at the same clampinglocation; clamp mechanisms, such as that described with respect to FIGS.1A and 1B, that clamp the sets of leads of a lead frame at differenttimes and at different clamping locations; and any combination thereof.It will also be understood that a wide variety of lead frames,including, for example, Leads-Over-Chip (LOC) lead frames andTapeUnder-Frame (TUF) lead frames, and any wire-bondable IC die, willwork in conjunction with the present invention.

As shown in FIG. 2A, a portion of a clamp mechanism in accordance withanother embodiment of the present invention includes a clamp block 30moving as directed by an actuating mechanism (not shown) in awire-bonding machine (not shown) to fixedly hold bus bar LOC leads 32 ofa LOC lead frame 34 against an IC die 36 attached to the LOC lead frame34 and supported by a heat block or other base (not shown). Once the busbar LOC leads 32 are fixedly held (i.e., clamped) by the clamp block 30,they may be wire-bonded using a wire bond tool (not shown) to selectedbond pads on a front-side surface of the IC die 36. Afterward, the clampblock 30 is moved away from the LOC lead frame 34 by the actuatingmechanism (not shown).

As shown in FIG. 2B, the bus bar LOC leads 32 of the LOC lead frame 34have been wire-bonded to bond pads on the IC die 36 while being clampedas described above and the clamp block 30 (FIG. 2A) has been moved awayfrom the LOC lead frame 34. Another portion of the clamp mechanism ofFIG. 2A includes a clamp block 38 moving as directed by the actuatingmechanism (not shown) of FIG. 2A to fixedly hold non-bus bar LOC leads40 of the LOC lead frame 34 against the IC die 36. Once the leads 40 arefixedly held by the clamp block 38, they may be wire-bonded through abonding aperture 42 in the clamp block 38 to bond pads on the front-sidesurface of the IC die 36 using the wire bond tool (not shown) of FIG.2A.

By clamping the bus bar LOC leads 32 and non-bus bar LOC leads 40 of theLOC lead frame 34 at different times in accordance with the presentinvention, the bus bar LOC leads 32 interposed between bond pads on thefront-side surface of the IC die 36 and the non-bus bar LOC leads 40 canbe filly clamped while they are wire-bonded. This is in contrast to theconventional clamping method described above which would only clamp theLOC leads 32 and 40 of the LOC lead frame 34 once, and thus would notfully clamp the bus bar LOC leads 32, since to do so while also clampingthe non-bus bar LOC leads 40 would interfere with the wire-bonding ofthe non-bus bar LOC leads 40.

It will be understood that the clamp mechanism of FIGS. 2A and 2B maytake a variety of forms, and that the present invention includes withinits scope all clamp mechanisms capable of clamping the LOC leads of aLOC lead frame in sets, one set at a time and in any order. It will alsobe understood that the clamp mechanism may comprise a variety of clampmembers, including, for example, one or more clamp blocks, as shown inFIGS. 2A and 2B, or one or more clamp fingers, as described below withrespect to FIG. 3B. It will further be understood that the clampmechanism may include one or more clamp members for clamping each set ofLOC leads in an LOC lead frame, and that each of the clamp members mayindividually clamp one or several LOC leads in the set. Further, it willbe understood that the present invention includes within its scope:clamp mechanisms that clamp all the sets of LOC leads of a LOC leadframe at different times but at the same clamping location, as shown inFIGS. 2A and 2B; clamp mechanisms, such as that shown in FIGS. 1A and1B, that clamp the sets of leads of a lead frame at different times andat different clamping locations; and any combination thereof.

As shown in FIG. 3A, a portion of a clamp mechanism in accordance with afurther embodiment of the present invention includes a clamp block 50moving as directed by an actuating mechanism (not shown) in awire-bonding machine (not shown) to fixedly hold LOC leads 52 of apartial LOC lead frame 54 against an IC die 56 attached to the partialLOC lead frame 54 and supported by a heat block or other base (notshown). Once the LOC leads 52 are fixedly held (i.e., clamped) by theclamp block 50, they may be wire-bonded through a bonding aperture 58 inthe clamp block 50 to selected bond pads on a front-side surface of theIC die 56 using a wire bond tool (not shown).

As shown in FIG. 3B, the LOC leads 52 of the partial LOC lead frame 54have been wire-bonded to bond pads on the IC die 56 while being clampedas described above and the partial LOC lead frame 54 has been indexed toa new clamping location with respect to the clamp mechanism of FIG. 3A.Another portion 60 of the clamp mechanism of FIG. 3A includes clampfingers 62 moving together as directed by the actuating mechanism (notshown) of FIG. 3A to fixedly hold non-LOC leads 64 of the partial LOClead frame 54 against the heat block or other base (not shown) in adifferent plane than the plane of the front-side surface of the IC die56. Once the non-LOC leads 64 are fixedly held by the clamp fingers 62,they may be wire-bonded using a wire bond tool (not shown) to bond padson the front-side surface of the IC die 56.

By clamping the LOC leads 52 and non-LOC leads 64 of the partial LOClead frame 54 at different times in accordance with the presentinvention, the LOC leads 52 and the non-LOC leads 64 can be fullyclamped while they are wire-bonded despite being clamped in differentplanes. This is in contrast to the conventional clamping methoddescribed above which would clamp the LOC leads 52 and the non-LOC leads64 at the same time, and thus may fail to fully clamp some of the leads52 and 64.

It will be understood that the clamp mechanism of FIGS. 3A and 3B maytake a variety of forms, and that the present invention includes withinits scope all clamp mechanisms capable of clamping the leads of apartial LOC lead frame in sets, one set at a time and in any order. Itwill also be understood that the clamp mechanism may comprise a varietyof clamp members, including, for example, one or more clamp blocks, asshown in FIG. 3A, or one or more clamp fingers, as shown in FIG. 3B. Itwill further be understood that the clamp mechanism may include one ormore clamp members for clamping each set of leads in a partial LOC leadframe, and that each of the plurality of clamp members may individuallyclamp one or several leads in the set. Further, it will be understoodthat the present invention includes within its scope: clamp mechanismsthat clamp all the sets of leads of a partial LOC lead frame atdifferent times but at the same clamping location; clamp mechanisms,such as that shown in FIGS. 3A and 3B, that clamp the sets of leads of alead frame at different times and at different clamping locations; andany combination thereof.

As shown in FIG. 4A, a portion of a clamp mechanism in accordance withan additional embodiment of the present invention includes a clamp block70 moving as directed by an actuating mechanism (not shown) in awire-bonding machine (not shown) to fixedly hold Tape-Under-Frame (TUF)leads 72 of a TUF lead frame 74 against a heat block or other base (notshown) by pressing against the front-side surface of an IC die 76attached to the TUF lead frame 74. Once the TUF leads 72 are fixedlyheld (i.e., clamped) by the clamp block 70, they may be wire-bonded toselected bond pads on the front-side surface of the IC die 76 using awire bond tool (not shown).

As shown in FIG. 4B, the TUF leads 72 of the TUF lead frame 74 have beenwire-bonded to bond pads on the IC die 76 while being clamped asdescribed above and the TUF lead frame 74 has been indexed to a newclamping location with respect to the clamp mechanism of FIG. 4A.Another portion 78 of the clamp mechanism of FIG. 4A includes clampblocks 80 moving together as directed by the actuating mechanism (notshown) of FIG. 4A to fixedly hold non-TUF leads 82 of the TUF lead frame74 against the heat block or other base (not shown). Once the non-TUFleads 82 are fixedly held by the clamp blocks 80, they may bewire-bonded using a wire bond tool (not shown) to bond pads on thefront-side surface of the IC die 76.

By clamping the TUF leads 72 and non-TUF leads 82 of the TUF lead frame74 at different times in accordance with the present invention, bothsets of leads 72 and 82 can be fully clamped while they are wire-bondeddespite being clamped in different planes. This is in contrast to theconventional clamping method described above which would clamp the TUFleads 72 and the non-TUF leads 82 at the same time, and thus may fail tofully clamp some of the leads 72 and 82.

It will be understood that the clamp mechanism of FIGS. 4A and 4B maytake a variety of forms, and that the present invention includes withinits scope all clamp mechanisms capable of clamping the leads of a TUFlead frame in sets, one set at a time and in any order. It will also beunderstood that the clamp mechanism may comprise a variety of clampmembers, including, for example, one or more clamp blocks, as shown inFIGS. 4A and 4B, or one or more clamp fingers, as shown in FIG. 3B. Itwill further be understood that the clamp mechanism may include one ormore clamp members for clamping each set of leads in a TUF lead frame,and that each of the plurality of clamp members may individually clampone or several leads in the set. Further, it will be understood that thepresent invention includes within its scope: clamp mechanisms that clampall the sets of leads of a TUF lead frame at different times but at thesame clamping location; clamp mechanisms, such as that shown in FIGS. 4Aand 4B, that clamp the sets of leads of a lead frame at different timesand at different clamping locations; and any combination thereof.

As shown in FIG. 5A, a portion of a clamp mechanism in accordance withyet another embodiment of the present invention includes a clamp block90 moving as directed by an actuating mechanism (not shown) in awire-bonding machine (not shown) to fixedly hold a first set of leads 92of a multi-level lead frame 94 against a heat block or other base (notshown) beneath the multi-level lead frame 94. Once the leads 92 arefixedly held (i.e., clamped) by the clamp block 90, they may bewire-bonded with a wire bond tool (not shown) inserted through a bondingaperture 98 in the clamp block 90 to selected bond pads on thefront-side surface of an IC die 96 attached at its backside surface tothe multi-level lead frame 94.

As shown in FIG. 5B, the leads 92 of the multi-level lead frame 94 havebeen wire-bonded to bond pads on the IC die 96 while being clamped asdescribed above and the multi-level lead frame 94 has been indexed to anew clamping location with respect to the clamp mechanism of FIG. 5A.Another portion of the clamp mechanism of FIG. 5A includes a clamp block100 moving as directed by the actuating mechanism (not shown) of FIG. 5Ato fixedly hold a second set of leads 102 of the multi-level lead frame94 against the heat block or other base (not shown). Once the leads 102are fixedly held by the clamp block 100, they may be wire-bonded with awire bond tool (not shown) inserted through a bonding aperture 104 inthe clamp block 100 to bond pads on the front-side surface of the IC die96.

By clamping the first set of leads 92 and the second set of leads 102 ofthe multi-level lead frame 94 at different times in accordance with thepresent invention, both sets of leads 92 and 102 can be fully clampedwhile they are wire-bonded despite being clamped in different planes.This is in contrast to the conventional clamping method described abovewhich would clamp the first set of leads 92 and the second set of leads102 at the same time, and thus may fail to fully clamp some of the leads92 and 102.

It will be understood that the clamp mechanism of FIGS. 5A and 5B maytake a variety of forms, and that the present invention includes withinits scope all clamp mechanisms capable of clamping the leads of amulti-level lead frame in sets, one set at a time and in any order. Itwill also be understood that the clamp mechanism may comprise a varietyof clamp members, including, for example, one or more clamp blocks, asshown in FIGS. 5A and 5B, or one or more clamp fingers, as shown in FIG.3B. It will further be understood that the clamp mechanism may includeone or more clamp members for clamping each set of leads in amulti-level lead frame, and that each of the clamp members mayindividually clamp one or several leads in the set. Further, it will beunderstood that the present invention includes within its scope: clampmechanisms that clamp all the sets of leads of a multi-level lead frameat different times but at the same clamping location; clamp mechanisms,such as that shown in FIGS. 5A and 5B, that clamp the sets of leads of alead frame at different times and at different clamping locations; andany combination thereof.

As shown in FIG. 6A, a portion 110 of a clamp mechanism in accordancewith a still further embodiment of the present invention includes clampblocks 112 moving as directed by an actuating mechanism (not shown) in awire-bonding machine (not shown) to fixedly hold a first set of leads114 of a multilevel, two-piece lead frame 116 against a heat block orother base (not shown) beneath the lead frame 116. Once the leads 114are fixedly held (i.e., clamped) by the clamp blocks 112, they may bewire-bonded with a wire bond tool (not shown) to selected bond pads onthe front-side surface of an IC die 118 attached at its backside surfaceto the lead frame 116.

As shown in FIG. 6B, the leads 114 of the lead frame 116 have beenwire-bonded to bond pads on the IC die 118 while being clamped asdescribed above and the lead frame 116 has been indexed to a newclamping location with respect to the clamp mechanism of FIG. 6A.Another portion 120 of the clamp mechanism of FIG. 6A includes clampblocks 122 moving as directed by the actuating mechanism (not shown) ofFIG. 6A to fixedly hold a second set of leads 124 of the lead frame 116against the heat block or other base (not shown). Once the leads 124 arefixedly held by the clamp blocks 122, they may be wire-bonded with awire bond tool (not shown) to bond pads on the front-side surface of theIC die 118.

By clamping the first set of leads 114 and the second set of leads 124of the lead frame 116 at different times in accordance with the presentinvention, both sets of leads 114 and 124 can be fully clamped whilethey are wire-bonded despite being clamped in different planes. This isin contrast to the conventional clamping method described above whichwould clamp the first set of leads 114 and the second set of leads 124at the same time, and thus may fail to fully clamp some of the leads 114and 124.

It will be understood that the clamp mechanism of FIGS. 6A and 6B maytake a variety of forms, and that the present invention includes withinits scope all clamp mechanisms capable of clamping the leads of amulti-level, two-piece lead frame in sets, one set at a time and in anyorder. It will also be understood that the clamp mechanism may comprisea variety of clamp members, including, for example, one or more clampblocks, as shown in FIGS. 6A and 6B, or one or more clamp fingers, asshown in FIG. 3B. It will further be understood that the clamp mechanismmay include one or more clamp members for clamping each set of leads ina multi-level, two-piece lead frame, and that each of the clamp membersmay individually clamp one or several leads in the set. Further, it willbe understood that the present invention includes within its scope:clamp mechanisms that clamp all the sets of leads of a multi-level leadframe at different times but at the same clamping location; clampmechanisms, such as that shown in FIGS. 6A and 6B, that clamp the setsof leads of a lead frame at different times and at different clampinglocations; and any combination thereof.

As shown in FIG. 7A, the clamp blocks 30 and 38 (not shown in FIG. 7A)of FIGS. 2A and 2B may be incorporated into a clamp mechanism 130 in awire-bonding machine 132. An indexing mechanism 134 in the machine 132sequentially indexes LOC lead frames in a lead frame strip 136 to acontact area on a heat block 138. While positioned proximate the contactarea, each LOC lead frame in the lead frame strip 136 is clamped usingthe clamp blocks 30 and 38 (not shown in FIG. 7A) of FIGS. 2A and 2B asdescribed above and is wire bonded as described above using a wirebonding tool 140 inserted through a bonding window 142 in the clampmechanism 130.

Also, a wire bond test device 144, such as a pull test device or a sheartest device, inserted through the bonding window 142 during wire bondingtests completed wire bonds once the wire bonding tool 140 moves on toother bonding sites.

It will be understood by those having skill in the field of thisinvention that a wide variety of indexing mechanisms and heat blockswill work for purposes of this invention. It will also be understoodthat the bonding machine 132 of FIG. 7A will work with any clampmechanism capable of clamping the leads of a lead frame in sets, one setat a time. Further, it will be understood that the wire bonding tool 140may comprise one or more bonding tools, including, for example,ultrasonic, thermosonic, and thermo-compression bonding tools.

As shown in FIG. 7B, the clamp blocks 90 and 100 (not shown in FIG. 7B)of FIGS. 5A and 5B may be incorporated into a clamp mechanism 150 in awire-bonding machine 152. An indexing mechanism 154 in the machine 152indexes lead frames in a lead frame strip 156 in turn to each of a pairof contact areas on a heat block 158. While positioned proximate thecontact areas, each lead frame in the lead frame strip 156 is clampedusing the clamp blocks 90 and 100 (not shown in FIG. 7B) of FIGS. 5A and5B as described above and is wire bonded as described above using a wirebonding tool system 160 including a pair of wire-bonding tools 162inserted through bonding windows 164 in the clamp mechanism 150.

Also, a wire bond test device system 166 including wire bond testdevices 168, such as pull test devices or shear test devices, insertedthrough the bonding windows 164 during wire bonding tests completed wirebonds once the wire bonding tools 162 move on to other bonding sites.

It will be understood by those having skill in the field of thisinvention that a wide variety of indexing mechanisms and heat blockswill work for purposes of this invention. It will also be understoodthat the bonding machine 152 of FIG. 7B will work with any clampmechanism capable of clamping the leads of a lead frame in sets, one setat a time. Further, it will be understood that the wire bonding tools162 may comprise any bonding tools, including, for example, ultrasonic,thermosonic, and thermo-compression bonding tools.

Although the present invention has been described with reference toparticular embodiments, the invention is not limited to theseembodiments. Rather, the invention is limited only by the appendedclaims, which include within their scope all equivalent devices ormethods that operate according to the principles of the invention asdescribed.

What is claimed is:
 1. A method for clamping leads of a lead frame, themethod comprising clamping a plurality of sets of the leads of the leadframe one set of leads at a time with each set of leads including fewerthan all the leads of the lead frame, at least one set of leads of theplurality of sets of leads including more than one of the leads and atleast one set of leads being clamped on a different plane than at leastone other set of leads.
 2. The method of claim 1, wherein the clampingone set of the leads at a time comprises holding said one set of theleads at a time against a heat block.
 3. A method for wire bonding leadsof lead frames in a lead frame strip to bond pads on integrated circuitdice attached to the lead frames, the method comprising: sequentiallyindexing each lead frame in the lead frame strip to a clamping position;clamping a plurality of sets of the leads of each lead frame indexed tothe clamping position one set at a time with each set of leads includingfewer than all of the leads of the lead frame, at least one setincluding more than one of the leads and at least one set of leads beingclamped on a different plane than at least one other set of leads; andbonding each set of clamped leads to bond pads on the integrated circuitdice attached to the lead frame of the clamped leads.
 4. The method ofclaim 3, wherein the bonding each set of clamped leads comprises bondingeach set of clamped leads using a bonding method selected from a groupcomprising ultrasonic bonding, thermosonic bonding, andthermo-compression bonding.
 5. The method of claim 3, furthercomprising: testing wire bonds of non-clamped leads of each lead frameindexed to the clamping position while other leads of the lead frame areclamped.
 6. The method of claim 5, wherein the testing wire bondscomprises at least one of pull testing and shear testing wire bonds. 7.A method of clamping a plurality of leads of a lead frame, each leadhaving a bonding region, the method comprising: subdividing a pluralityof leads into at least two sets of leads based on a distance betweentheir respective bonding regions and a center portion of the lead frame;and clamping each set of leads one set of leads at a time.
 8. The methodof claim 7, wherein clamping the leads one set of leads at a timefurther comprises clamping the leads one set at a time in an orderaccording to which set has the shortest distance between theirrespective bonding regions and the center portion of the lead frame. 9.The method of claim 7, wherein the lead frame includes bus bars and oneset of leads includes solely bus bars.
 10. The method of claim 9,wherein the set of leads including only bus bars is clamped first.
 11. Amethod of clamping a plurality of leads of a lead frame, at least onelead lying in a different plane than at least one other lead, the methodcomprising: subdividing a plurality of leads into at least two sets ofleads based on the plane in which they lie; and clamping each set ofleads one set of leads at a time.
 12. The method of claim 11, whereinthe plurality of leads includes leads-over-chip type leads and whereinsubdividing the plurality of leads includes creating a set of leadsincluding only the lead-over-chip type leads.
 13. The method of claim12, wherein clamping the sets of leads one set at a time furtherincludes clamping the set of lead-over-chip type leads first.
 14. Themethod of claim 11, wherein the plurality of leads includestape-under-frame type leads and wherein subdividing the plurality ofleads includes creating a set of leads including only tape-under-frametype leads.
 15. The method of claim 14, wherein clamping the sets ofleads one set at a time further includes clamping the set oftape-under-frame type leads first.
 16. A method for wire bonding leadsof lead frames in a lead frame strip to bond pads on integrated circuitdice attached to the lead frames, the method comprising: sequentiallyindexing each lead frame in the lead frame strip to a clamping position;clamping a plurality of sets of the leads of each lead frame indexed tothe clamping position one set at a time with each set of leads includingfewer than all of the leads of the lead frame and at least one setincluding more than one of the leads; bonding each set of clamped leadsto bond pads on the integrated circuit dice attached to the lead frameof the clamped leads; and testing wire bonds of non-clamped leads ofeach lead frame indexed to the clamping position while other leads ofthe lead frame are clamped.
 17. The method of claim 16, wherein thetesting wire bonds comprises at least one of pull testing and sheartesting wire bonds.